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Fb. 1, 1955 J. J. coUGHLlN Re. 23,932

ELECTRONIC PHASE SHIFTING APPARATUS Original Filed Feb. 2.3, 1951 3 Sheets-Sheet l @j we@ f/ AZ 5% ji l .mu/swf WHKE ('Gi/Yikf /z Jfmltm Feb. l, 1955 1 J, COUGHLIN I Re. 23,932

ELECTRONIC PHASE SHIFTING APPARATUS original Filed Reb. 25, 1951 s sheets-sheet 2 l l l l n u l u Q b j, Y

: l:L I #T I iur" INVENTQR I Feb. 1, 1955 Original Filed Feb. 25, 1951 e J. J. COUGHLIN ELECTRONIC PHASE SHIFTING APPARATUS JfgNv-A 3 Shee ts-Sheet 3 INVENTOR United States Patent Otice Re. 23,932 Reissued Feb. 1, 1955 ELECTRONIC PHASE SHIFTING APPARATUS Joseph J. Coughlin, Rochelle Park, N. J., assignor to Radio Corporation of America, a corporation of Delaware Original No. 2,617,932, dated November 11, 1952, Serial No. 212,269, February 23, 1951. Application for reissue March 12, 1953, Serial No. 342,041

lll Claims. (Cl. Z50-27) Matter enclosed in heavy brackets appears in the original patent but forms no part of this reissue specification; matter printed in italics indicates the additions made by reissue.

The present invention relates to phase shifting systems and more particularly to a novel system for shifting the phase of a timing wave generated by a timing generator for local apparatus to follow an incoming signal that has no special elements for synchronizing [sync pulses] In accordance with the invention, two space discharge devices have a common anode resistor but different control electrode inputs driven by local trigger circuits. A square wave source is provided which causes operation ot' a local timing generator. The square wave is blanked by causing conduction of either of the space discharge devices. Blanking performs two functions in apparatus embodying the invention. It blanks out the square wave for the required interval or intervals; and it alters the wave shape of the wave from the square wave source.`

This results in the subtraction or addition of cycles or pulses during the correction interval.

An object of the present invention is to provide a novel phase shifter for maintaining the local synchronization with incoming signals which do not have transmitted sync pulses. l

A further object is to provide novel means for shaping and differentiating the wave from a signal generator, such as a limiting amplifier or counter circuit.

Other objects and advantages of the invention will, of course, become apparent and immediately suggest themselves to those skilled in the art to which this invention is directed from a reading of the following specification in connection with the accompanying drawing in which:

Fig. l is a schematic showing of phase shifting apparatus embodying the present invention;

Fig. 2 shows curves illustrating operation of the appal ratus of Fig. l when correction or phase shift is not required;

Fig. 3 shows curves illustrating operation of the apparatos when advance correction is eifective;

Fig. 4 is similar to Fig. 3 and shows curves illustrating operation of the apparatus when correction takes place on the other phase of the square wave; and

Figs. 5 and 6 are similar in their Showing to Figs. 3 and 4 but illustrate operation of the apparatus when retard correction is elifective.

Fig. l of the drawing shows, illustratively, apparatus embodying the invention for shifting the phase of the output wave of a timing generator 10 which may be operative to control or time equipment (not shown) such as a telegraph system or the like. The controlled equipment is to operate, in the illustrative example, in synchronism with received signals of such character that they do not have separate sync (synchronizing) signals. [Close synchronism is maintained by a] A square wave generator 12 of any known kind or type [which] converts the output ot a standard frequency source, for example, applied at terminals 16 and 18, to a suitably shaped rectangular 0r square-sided pulsating [the] wave form 21 shown in Fig. 2a. The standard frequency source may be of any known type. It may be a tuning fork or crystal controlled compensated oscillator which generates waves of sinusoidal form. The square wave generator may be an amplitude limiting amplifier or it may be a well-known multivibrator triggered from the wave or pulses derived from the standard frequency source. An amplierof the kind mentioned is disclosed in Artzt Patent No. 2,383,360 granted August 2l, 1945.

The square wave output 21 from the square wave generator or limiter 12 is applied through a coupling condenser 24 to an element of a repeater device such 0S the control electrode or grid 25 of a vacuum tube 26. It will be understood that a suitable voltage supply and bias source (not shown) is provided for the apparatus of Fig. l. Since operating and bias potential sources for the apparatus of Fig. l [is] are not a distinct part of the present invention, they are not shown in detail. The anode 27 ot' the tube 26 is connected through a load resistor 28 to the positive terminal of the supply source as indicated schematically by terminal 29. The cathode 32 of the tube 26 is returned to a point in the system which is negative with respect to ground as indicated by the legend -B. Ground is assumed to be the reference point for the system.

The anode 36 of [the] a second repeater device SllCh as a vacuum tube 38 is directly connected to the anode 2'7 of the tube 26. The cathode of the tube 33 is rcturned to ground through a cathode resistor 41. Two control devices such as the vacuum tubes 44 and 46 have their plates or anodes connected through a common plate load resistor 48 to the source of positive potential as indicated schematically by the terminal 51. The grid 53 of the tube 38 is connected to the anodes of the tubes 44 und 46. The grid 56 ot' the tube 44 is connected through a series resistor 5S and a resistor 59 to a point of negative biasing potential as indicated schematically at the terminal 61. Similar' resistors 63 and 64 serve the same purpose for the grid 66 of the tube 46. The source of biasing potential at the terminal 61 is suiciently negative normally to cut oit the tubes 44 and 46.

The voltage appearing across the resistor 41 is coupled by way of a condenser 63 to the input circuit of the timing generator 10. The condenser 68 in conjunction with a resistor 71 serves to dilerentiate the square Wave pulses developed across the resistor 41 to produce a pulse at euch impulse of the wave. As indicated by Fig. 1 of the drawing, the timing generator 10 is shown, illustrative1y,` as being in the form. of a flip-flop multivibrator having two tubes 74 and '76, coupled as shown. The resistor-condenser combinations 78 and 79, one in each cross-coupling circuit, decreases the switching time of the multivibrator and the value of the condenser ineluded in each combination changes the sensitivity to plus or minus pulses. It will be understood that the timing generator may include one or more stages intercoupled to provide a counting system of the type by now well known in the prior art. Electronic apparatus employing multivibrators similar to those shown illustratively in Fig. l of the drawing are discussed in an article entitled Electronic digital counters by Warren H. Bliss appearing in the April 1949 issue of Electrical Engineermg.

The normally non-conducting tubes 44 and 46 may each become conductive under control of its respective pulse producing trigger circuit 81 or S2. The trigger 81 is the advance trigger which operates when the phase of the timing generator is to be advanced. The retard trigger 82 operates when the phase of the timing gcnerator is to be retarded. The advance trigger 81 is shown as being in the form of a well-known one-shot multivibrator comprising coupled tubes 84 and S6. The time duration of the square-topped pulse produced by the advance trigger 81 is controllable by adjustment of the resistor 88. Signals or pulses for initiating operation of the advance trigger circuit 81 may be applied to the terminal 91 through a coupling condenser 92 to the grid 94 of the tube 84. A similar connection for the retard trigger 82 is indicated by reference character 96.

Operation of the apparatus of Fig. 1 by means of which close synchronsm is maintained in accordance with the invention will now be described. Phase shifting is accomplished by blankng out a section of the square 3 Wave 21 before diiisrsntiaticn by the lis-Q circuit 7k-635. The time interval of blanking is different for advance and retard. The blanking process set forth herein as a feature ci the invention alters the Wave shape Sc as to always add two pulses when differentiated. ,Referring to Fig. l, tubes 44 and 46 are normally cut-off. They conduct only when the locally generated retard or advance pulses exist. advance pulse is shown by Fig. 3a and t is indicated as occupying the time interval ta. A retard pulse is shown by way of example in Fig. 5a and is shown as occupying the time tr. Since thetubes 44 and 46 are non-conducting, the grid 53 of the tube 38 is returned to +B through the resistor 48. Bccause of the voltage divider action of the resistor 48, conducting grid resistance of the tube 38, and the resistor 41, there is a positive D.C. voltage on the cathode of the tube 38. Referring to Fig. 2a of the drawings, this voltage is represented by the [peaks] troughs 101 of the wave l21 when the voltage at the anode 36 is equal to or less than zero. The square wave generated in the tube `26 across the resistor 2S is applied to the anode 36 of the tube 38. When the tube 26 is non-conducting, the tube 38 draws plate current, and conversely, when the tube 26 is conducting the tube 38 draws no plate current. tube 38, the cathode voltage increases in a positive direction to the peaks 103 of the wave 21. The output of the tube 38 is differentiated as indicated in Fig. 2b and the resulting pulses are applied to the local timing generator lll. This is done in the illustrative example by means of coupling condensers 106 and 107. The differentiated pulses are of considerable amplitude and thereby both the positive and negative differentiated pulses are effective to operate the timing generator 10. When correction is required, the advance trigger 81 or the retard trigger 8 2 is operated. Let it be assumed that a pulse 109 is derived from the apparatus (not shown) to be controlled from the timing generator 10. This pulse Will lire the advance trigger and a pulse of time duration ts (Fig. 3a) appears in the grid 56 of the tube 44. This causes the tube 44 to conduct. The plate voltage goes sufiiciently With plate current in the o negative to cut off the tube 38. This causes its cathode voltage to go to zero. The result is a wave shape as shown in Fig. 3a. Since correction can take place on either phase of the square wave, both possibilities are shown. Fig. 3a and Fig. 4a illustrate these possibilities. The differentiated pulses are shown in Fig. 3b. Fig. 3c shows the action of the locking or counting circuit of the timing generator 10 compared to the normal action without correction which is shown in Fig. 3d. For the local timing generator 10 to advance with respect to the signal,

the local advance trigger 81 operates for a time ta where ts is greater than t1 and less than 2t1. In Fig. 3b, the normal pulse, now missing, 'is shown dotted While the pulses due to the operation of the advance trigger are designated 112 and 114. From this it will be seen that one pulse is omitted and two new ones are added, hence, the iinal result is the addition of one pulse.

When the local retard trigger 82 operates or res, it couples a pulse of time duration tr (Fig. 5a) onto the grid of the tube 46 causing this tube to conduct. Its action is similar to the local advance trigger 81 except that the time interval tr is greater than the time interval ts. Fig. 5a shows the voltage on the cathode of the tube 38. Fig. 5b shows the differentiated pulse output. Fig. 5c shows the action of the local timing generator 10 with correction as compared to that without correction in Fig. 5d. The time interval of the local retard trigger tr is greater than three times t1 and less than four times t1.

Fig. 5b shows that three normal pulses are missing due to the blanking out of the square wave for the time tr. The local retard trigger in operating as in the case of the local advance trigger adds two pulses, hence, one pulse is omitted. This causes the local timing generator to be retarded with respect to the incoming signal.

What is claimed is:

l. Phase shifting apparatus comprising means to provide an alternating current input signal, means to convert said signal to square wave form, means for repeating said` square Wave signals, a second repeater, a timing generator. an. output connection from said second repeater to said timing generator, a control tube, means coupling said control tube to said second repeater to control repeater operation, and timing means for causing said control tube (to become conductive for a predetermined time perlo 2,. Phase sh tina apparatus comprising means .to pro- Vvide an alternating current input signal, means to convert said signal to square wave form, means for repeating said square wave signals comprising a tube having a cathode, an anode and a control electrode, a second repeater comprising a tube having a cathode, an anode and a control electrode, a timing generator, an output connection from the cathode of said second repeater to said timing generator, a control tube, means coupling said control tube to the control electrode of said second repeater to control repeater operation and a multivibrator for causing said control tube to become conductive for a predetermined time period.

3. Phase shifting apparatus comprising means to provide an alternating current input signal, means to convert said signal to Square wave form, means for repeating said square wave signals comprising a tube having a cathode and a control electrode, a second repeater cornprising a tube having a cathode, an anode and a control electrode, a multivibrator, an output connection from the cathode of said second repeater to said multivibrator, a control tube, means coupling said control tube to the control electrode of said second repeater to control repeater operation, and a second multivibrator of the one-shot type for causing said control tube to become conductive for a pldetermined time period.

4. Phase shifting apparatus comprising means to provide an alternating current input signal, means to convert said signal to square wave form, a repeater for repeating said square wave signals comprising a tube having an anode, a cathode, and a control electrode means to couple said control electrode to said first-named means, a resistor connecting said anode to a positive direct current source, a second tube having an anode, a cathode and a control electrode, a connection from the anode of said second tube to the anode of said lirst tube, a pair of control tubes each of which includes an anode, a cathode and a control electrode, a resistor connecting the anodes of said control tubes to said positive direct current source, a connection from said anodes of said control tubes to the control electrode of said second tube, a trigger circuit coupled to the grid of one of said control tubes, a second trigger circuit coupled to the grid of the other control tubes, each trigger circuit having means to cause the control tube to which it is connected to become conductive.

5. Phase shifting apparatus comprising means to pro vide an alternating current input signal, means to convert said signal to square wave form, a repeater for repeating said square wave signals comprising a tube having an. anode, a cathode and a control electrode, means to couple said control electrode to said first-named means, a resistor connecting said anode to a positive direct current source, a second tube having an anode, a cathode and a control electrode, a connection from the anode of said second tube to the anode of said irst tube, a control tube including an anode, a cathode and a control electrode, a resistor connecting the anode of said control tube to said positive direct current source, a connection from said anode of said control tube to the control electrode of said second tube, a trigger circuit coupled to the grid of said control tube, said trigger circuit having means to cause said control tube to become conductive whereby to cause cutoff of said second tube and a decrease in the cathode voltage thereof, the catllodes of said rst tube and said pair of control tubes being connected to a voltage reference point in said system, a resistor connecting the cathode of said second tube to a voltage reference point in said circuit which is less negative than the voltage reference polint of the connection of the cathode of said rst-named tu e.

6. Phase shifting apparatus comprising means to provide an alternating current input signal, means to convert said signal to square wave form, a repeater for repeating said square wave signals comprising a tube having an anode, a cathode, and a control electrode. means to couple said control electrode to said rst-named means, a resistor connecting said anode to a positive direct cur- `rent source, a second tube having an anode, a cathode and a` control electrode, a connection from the anode of said second tube to the anode of said first tube, a control tube including an anode, a cathode and a control electrodc, a resistor connecting the anode of said control tube to said positive direct current source, a connection from said anode of said control tube to the control electrode of said second tube, a trigger circuit coupled to the grid of said control tube, said trigger circuit having means to cause said control tube to become conductive whereby to cause cutoff of said second tube and a decrease in the cathode voltage thereof, the cathode of said rst tube and said control tube being connected to a voltage reference point in said system, a resistor connecting the cathode of said second tube to a voltage reference point iu said circuit which is less negative than the voltage reference point of the connection of the cathode of said first-named tube, a timing generator, means for coupling the cathode of said second tube to said timing generator, means to supply a control pulse to said rst trigger circuit, and means to supply a control pulse to said second trigger circuit.

7. Phase shifting apparatus comprising means to provide an alternating current input signal, means to convert said signal to square Wave form, a repeater for repeating said square wave signals comprising a tube having an anode, a cathode, and a control electrode, means to couple said control electrode to said rst-named means, a resistor connecting said anode to a positive direct current source, a second tube having an anode, a cathode and a control electrode, a connection from the anode of said second tube to the anode of said rst tube, a pair of control tubes each of which includes an anode, a cathode and a control electrode, a resistor connecting the anodes of said control tubes to said positive direct current source, a connection from said anodes of said control tubesto the control electrode of said second tube, a trigger circuit coupled to the grid of one of said control tubes a second trigger circuit coupled to the grid of the other control tube, each trigger circuit having means to cause the control tube to which it is connected to become con ductive whereby to cause cutoff of said second tube and a decrease in the cathode voltage thereof, the cathodes of said rst tube and said pair of control tubes being connected to a voltage reference point in said system, a resistor connecting the cathode of said second tube to a voltage reference point in said circuit which is less negative than the voltage reference point of the connection of the cathode of said first-named tube, a timing generator, means for coupling the cathode of said second tube to said timing generator, means to supply a control pulse to said iirst trigger circuit, and means to supply a control pulse to said second trigger circuit.

8. Apparatus for eectively shifting the phase of a pulsating waveform, including a device lfor repeating said pulsating waveform, a differentiating circuit coupled to the output of said repeating device to produce a pulse at each impulse of said pulsating waveform, a timing generator under the control of said differentiating circuit and responsive to pulses of current to produce a pulsating waveform normally corresponding to the rst said pulsating waveform, a control device coupled to said repeating device for blanking a portion of the rst said pulsating waveform to introduce additional impulses in the output of said repeater device, and timing means coupled to said control device to space said additional impulses in time to result in the addition or subtraction of pulses from the pulsating waveform produced by said timing generator.

9. Apparatus for effectively shifting the phase of a pulsating waveform, including a device for repeating said pulsating waveform, a dierentiating circuit coupled to the output of said repeating device to produce a pulse at eac/1 impulse of said pulsating waveform, a timing generator under the control of said dierentiating circuit and responsive to pulses of current to produce a pulsating waveform normally corresponding to the first said pulsating waveform, a control device coupled to said repeating device to introduce additional impulses in the output of said repeater device, and timing means coupled to said control device to space said additional impulses in time to result in the addition or subtraction of pulses from the pulsating waveform produced by said timing generator.

10. Apparatus for eectively shifting the phase of a pulsating waveform, including a normally conducting vacuum tube having a cathode, a control electrode and an anode for repeating said pulsating waveform, a differentiating circuit comprising a capacitor and a resistor coupled to the cathode of said vacuum tube to produce a pulse at each impulse of said pulsating waveform, a timing generator responsive to pulses of current to produce a pulsating waveform under control of said dierentiating circuit, a normally blocked control tube having a cathode, a control electrode and an anode coupled to the control electrode of said vacuum tube to block the latter and thereby introduce additional impulses in the output of said vacuum tube, and timing means coupled to the control tube to render said control tube conducting for a predetermined period of time to result in the addition or subtraction of pulses from the pulsating waveform produced by said timing generator.

References Cited in the file of this patent or the original patent UNITED STATES PATENTS 2,435,207 Dimond Feb. 3, 1947 2,466,044 Schoenfeld Apr. 5, 1949 2,514,369 Buehler July l1, 1950 2,538,027 Mozley et al. Ian. 16, 1951 2,558,358 Hales June 26, 1951 2,564,559 Canfora Aug. 14, 1951 2,599,586 Ross June 10, 1952 

